If I hadda guess, it's a drive belt shifter.

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On 23 May 2004 23:25:38 GMT, (Fdmorrison) wrote:

(GTO69RA4)

Davis lathe

I don't know very much about lathe history, but one thing I've never seen is
that big lever on the headstock. It seems to internally swtich the first
stage
of feed gearing among three ratios. Like the predecessor of the quickchange
gearbox. This lathe relys mostly on change gears.

It could be a clutch that engages the spindle gear with the stud gear out to
the rest of the change gearing.

The lathe is in the "modern" configuration for gearing, having the leadscrew
and feed rod combined.
I don't recall from the pics, but you will have to find the left-end bearing
box for the leadscrew (right end is still there), and with that the
brackets/setup to get the gear set on the end of the leadscrew meshing with the
rest of the change-gear train.
Looks like it does not have power cross feed, only power long.
Frank Morrison